Planned Obsolescence in Software

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Planned Obsolescence Built to Last, or Build One to Throw Away? OSCON 2013 Baq Haidri • @baqhaidri Ian Dees • @undees

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Baq making things work at scale

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discoverable REST APIs http://rest.li/

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Ian tinkering with hardware and software

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http://pragprog.com/titles/dhwcr discount code: CucumberIanDees

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So, planned obsolescence

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OSCON 2012

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— Should software makers apply the planned- obsolescence strategy? — Like, a self-destructing Github repo? — More like designing things for the correct lifespan.

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Computer programs are... machines with far more moving parts than any engine: the parts don’t wear out, but they interact and rub up against one another in ways the programmers themselves cannot predict. —James Gleick

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Over-engineering

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Project needs this:

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ANTLRParser.new

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Engineer ships this:

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def create_parser xml = read_ridiculously_long_xml_file config = hash_from_xml(xml) type = config["type"] case type when "ANTLR" then ANTLRParser.new when "yacc" then YACCParser.new else raise "Unknown parser #{type}" end end

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Why do we do this?

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We imagine our software will be around forever

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Life of an Engineer

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1. n00b 2. Second-system effect 3. Too clever by half 4. Realism 5. Nirvana

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1. n00b

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10 PRINT "HELLO WORLD" 20 END

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Feature spree

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GPIBDevice::GPIBDevice(int newAddress) : address(newAddress) { // bunch of options code... }

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GPIBDevice::GPIBDevice(int newAddress, int newSecondary) : address(newAddress), secondary(newSecondary) { // bunch of options code... }

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GPIBDevice::GPIBDevice(int newAddress, int newSecondary, double newTimeOut, bool txEoi) : address(newAddress), secondary(newSecondary), timeout(ConvertTimeout(newTimeout)), sendEoi(txEoi) { // bunch of options code... }

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GPIBDevice::GPIBDevice(int newAddress, int newSecondary, double newTimeOut, bool txEoi, bool sendCr, bool sendLf, bool expectCr, bool expectLf, int bufSize, short newId) : address(newAddress), secondary(newSecondary), sendEoi(txEoi), sendReturn(sendCr), sendLinefeed(sendLf), expectReturn(expectCr), expectLinefeed(expectLf), bufferSize(bufSize), id(newId), pBuffer(NULL), receiveLength(0) { // bunch of options code... }

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The cost [of adding a feature] also includes the addition of an obstacle to future expansion.... You will usually wind up with a codebase that is so fragile that new ideas that should be dead-simple wind up taking longer and longer to work into the tangled existing web. The trick is to pick the features that don’t ﬁght each other. —John Carmack

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GPIBDevice::GPIBDevice(GPIBOptions options) { // ... }

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The right abstraction wasn’t obvious at ﬁrst

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What happens when...

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You are asked to build this

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But you want to build this!

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public class Voltron { public Voltron setType(Type type) {} public Voltron setColor(Color color) {} List getParts() {} public static void main(String[] args) { Voltron v = new Voltron(); v.setColor(YELLOW).setType(LION).render(); } }

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“Hey, this needs to be more general!”

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public class Voltron extends Robotron { // ... public static void main(String[] args) { Voltron v = new Voltron(); v.setColor(YELLOW).setType(LION).render(); } }

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public abstract class Robotron implements Transformable { @Override public Robotron render() { for (Part part : this.getParts()) { part.render(); } return this; } // ... }

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public interface Transformable extends Renderable { T setType(Type type); T setColor(Color color); List getParts(); }

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This ﬂexibility wasn’t a project requirement

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Good frameworks are extracted, not invented. —David Heinemeier Hansson

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What about one-offs?

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This is okay

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You look back at all the projects you’ve ever been on, and you can’t think of a single piece of code that wasn’t rewritten at least once, maybe half a dozen times, over the years. —Steve Yegge, http://bit.ly/yegge-mystery-3d

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One-offs teach us to abstract

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class BrewerTest : public CoffeeTest { public: bool testBrewing() { brewer.brew(); COFFEE_ASSERT(brewer.brewed()); } };

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class BrewerTest : public CoffeeTest { public: bool testBrewing() { brewer.brew(); COFFEE_ASSERT(brewer.brewed()); } };

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class BrewerTest : public Test { public: bool testBrewing() { brewer.brew(); ASSERT(brewer.brewed()); } };

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Don’t be afraid to use this!

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Or this!

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Or this!

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There is one ongoing project, even in one-offs:

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YOU

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2. Second-system effect

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class CHello : public CHelloBase { public: IPFIX(CLSID_CHello); CHello(IUnknown *pUnk); ~CHello(); HRESULT __stdcall PrintSz(LPWSTR pwszString); private: static int cObjRef; };

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How engineers measure our self-worth

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Ability to tackle complexity

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So we invent extra complexity

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class Adder def add(a, b) space = \ @antlr_parser.curr_node.space_needed do_stuff_to(a, space) do_stuff_to(b, space) result = \ @antlr_parser.curr_node.mkspace(space) result.fill_with(a + b) end end

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class Adder def add(a, b) space = \ @antlr_parser.curr_node.space_needed do_stuff_to(a, space) do_stuff_to(b, space) result = \ @antlr_parser.curr_node.mkspace(space) result.fill_with(a + b) end end

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“I can handle it”

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Anticipate the WTF? factor

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“Just because I can... should I?”

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“Would I want to support this?”

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Because you’re going to!

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Have the courage to decide provisionally

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3. Too clever by half

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#include #define S "Hello, World\n" main(){exit(printf(S) == strlen(S) ? 0 : 1);}

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Over-applying DRY

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it "converts to Fahrenheit" do zero_c.fahrenheit.must_equal(32.0) end it "converts to Kelvin" do zero_c.kelvin.must_equal(273.0) end

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it "converts to Fahrenheit" do zero_c.fahrenheit.must_equal(32.0) end it "converts to Kelvin" do zero_c.kelvin.must_equal(273.0) end

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[["Fahrenheit", 32.0], ["Kelvin", 273.0]].each do |units, expected| it "converts to #{units}" do method = units.downcase.to_sym actual = celsius.send(method) actual.must_equal(expected) end end

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And if you really have a lot of data...

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Celsius Fahrenheit Kelvin 0 32 273 100 212 373

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Use a table!

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| Celsius | Fahrenheit | Kelvin | | 0 | 32 | 273 | | 100 | 212 | 373 |

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Choose the right idiom for the environment

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def first_after(day) @table.find { |m| m.day > day } || no_meas end

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measurement* found = find_if(table, table + size, compose1( // f(g(pair)), where: bind2nd(greater(), day), // f(num) is "num > day?" select1st())); // g(pair) is "pair.first" return found ? *found : no_meas;

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Fear of the for loop

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for (int i = 0; i < size; ++i) { if (table[i].first > day) { return table[i]; } } return no_meas;

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4. Realism

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echo "Hello, world."

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We make discoveries, we autotune

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A generic probabilistic metaheuristic for the global optimization problem of locating a good approximation to the global optimum of a given function in a large search space. —http://en.wikipedia.org/wiki/Simulated_annealing

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Interfaces don’t require multiple implementations

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class WORNStorage { public: void write(const char* k, void* v) { // poke hardware registers } };

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int answer = 42; storage->write("answer", &answer);

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class Storable { public: virtual ~Storable() {} virtual void write(const char* k, void* v) = 0; }; class WORNStorage : public Storable { public: virtual void write(const char* k, void* v) { // poke hardware registers } };

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Testability

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class FakeStorage : public Storable { public: virtual void write(const char* k, void* v) { // DO NOTHING! } }; FakeStorage fake; someFunctionThatStores(fake);

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Convenience

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Storable* getStorableFromSomewhere() { return new WORNStorage(); }

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Conway’s Law and how to use it to your advantage

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Organizations which design systems... are constrained to produce designs which are copies of the communication structures of these organizations. —Melvin Conway

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“We’re screwed. The design is going to be bureaucratic and dysfunctional, just like our team.” The Pessimist:

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The Opportunist: “Sweet. If we organize the team like so, the design will naturally fall out the way we want it to.”

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Bad programmers worry about the code. Good programmers worry about data structures and their relationships. —Linus Torvalds

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Don’t solve organizational problems with technical solutions

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Know your needs

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Chances are, someone has already done it

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If you can get 90 percent of the desired effect for 10 percent of the work, use the simpler solution. —Bob Scheiﬂer and Jim Gettys

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class Project < ActiveRecord::Base has_many :documents end class Document < ActiveRecord::Base belongs_to :project end

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get '/' do haml :index end get '/projects/:id' do @project = Project.find params[:id] haml :project end

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@@index %ul - Project.all.each do |pj| %li %a{:href => "/projects/#{pj.id}"} = pj.name @@project - @project.documents.each do |d| %li= d.title

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This was not “built to last”

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...but it did anyway!

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I LOVE IT WHEN A PLAN COMES TOGETHER

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5. Nirvana

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All the universal truths:

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Chicken sexing

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Chicken sexing The experts had no idea how they had acquired their skills in the ﬁrst place, or how to transmit those skills to others. —Richard Horsey

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Chicken sexing We require training, or a great deal of detailed observation, in order for us to notice the relevant features, and thereby allow our unconscious mechanisms to acquire the diagnostic cues —Richard Horsey

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When to abstract?

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1. You know in advance e.g., multiple protocols

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2. You’re writing a library but what % of your projects are libraries?

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What makes a good abstraction?

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We control complexity by building abstractions that hide details when appropriate. —Harold Abelson and Gerald Sussman

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Hadoop

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public interface Mapper /* ... */ { void map(K1 key, V1 value, OutputCollector output, Reporter reporter) throws IOException; }

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If you need something once, build it. If you need something twice, pay attention. If you need it a third time, abstract it. —Derick Bailey

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Fundamentals

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More! https://github.com/undees/oscon @baqhaidri @undees

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